Indexing means and conveyors for use therewith

ABSTRACT

Indexing means are disclosed that have a support reciprocable by power operated means lengthwise of a conveyor between two limits and provided with conveyor grabbing means. Means are also provided to lock the conveyor against movement during dwells. Control means provide that on movement of the support in one direction the grabbing means are operated to cause the conveyor to be pulled thereby to complete a step and then to render the locking means operative for a predetermined interval during which the support is returned for another step. The travel of the support is adjustable and is controlled to provide for its acceleration and deceleration at the beginning and end of each step. The conveyor is shown as including both hold-down and supporting conveyors, each including two transversely spaced pairs of endless chains with the chain grabbing means including devices at each side of the conveyor, each receiving the outer chains of the proximate courses and operable to clamp them together. The proximate course of the inner chains of the holddown conveyor are yieldably urged into material gripping relationship with the corresponding chains of the proximate course of the supporting conveyor.

United States Patent Snow et al. Sept. 5, 1972 [54] INDEXING MEANS ANDCONVEYORS FOR USE THEREWITH Primary Examiner-Allen N. Knowles [7 2]Inventors: Gerald A. Snow, 5 Pine Ridge Road, Attorney-Abbott SpearCumberland Foreside, Maine 04092; Hamid A. Doughty, Eastman [571ABSTRACT Road, p Elizabeth, Maine Indexing means are disclosed that havea support 04107; Charles Allard, 12 reciprocable by power operated meanslengthwise of a Old Orchard Beach Mame conveyor between two limits andprovided with con- 04064;.Cha1'k5 f' veyor grabbing means. Means arealso provided to Houls Cent", 43111804042 lock the conveyor againstmovement during dwells. [22] Filed: Aug. 19, 1970 Control means providethat on movement of the support in one direction the grabbing means areoperated [21] Appl 64979 to cause the conveyor to be pulled thereby tocomplete a step and then to render the locking means [52] US. Cl..226/162, 226/172 operative for a predetermined interval during which[51] Int. Cl. ..B65h 17/26 the support is returned for another step. Thetravel of, Field of Search the support is adjustable and is controlledto provide 226/17 172 for its acceleration and deceleration at thebeginning and end of each step. The conveyor is shown as in- ReferencesCited I eluding both hold-down and supporting conveyors, UNITED STATESPATENTS each including two transversely spaced pairs of endless chainswith the chain grabbing means mclud- 2,908,378 10/1959 Bl'OWl'l 6t 81...198/135 ing devices at each side of the conveyor each receiv-2,586,630 2/1952 Erland 6t 81. ..198/203 ing the outer chains of theproximate courses and 2,720,963 10/ Stanley et 135 operable to clampthem together. The proximate 3,310,849 3/1967 Hazelett et a1 ..226/ 172X course f the inner chains f the holddown conveyor Granath 198/ areurged into material relationship 3,006,520 10/ 1961 House ..226/170 Xwith the corresponding chains of the proximate course 3,429,493 2/1969Lehmann ..226/162 X of the supporting conveyon 3,082,859 3/1963 l-lagneret al. ..198/135 3,420,037 l/l969 Villemure et al. .....l98/l 35 X 21Claims, 20 Drawing figures PATENTEDSEP 51912 3.688.963

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Jifi'o? INDEXING MEANS AND CONVEYORS FOR USE THEREWITH The presentinvention relates to conveyor indexing means and conveyors for usetherewith.

In the production of many articles, it is necessary to effect theiradvance step-by-step in order that successive operations can beperformed thereon during dwells. Where these operations require that thearticles be exactly positioned, indexing presents problems.

By way of example, the production of molded articles from plastic sheetmaterial requires a conveyor to advance a sheet through a heatingstation to a forming station where it is subjected to the action ofcoacting, article-forming molds and finally, after the sheet and thearticles formed therein have become sufficiently cooled to avoidwarping, to a blanking station where the articles are die-cut therefrom.For production purposes, the article forming and blanking stations arespaced apart by a distance representing a number of steps making itpossible to provide an intermediate station for additional operationssuch, for example, as printing. In practice, it is necessary to use, forthis type of production, supporting and hold-down conveyors to preventwarping. Such conveyors comprise transversely spaced, endless chains.

In US. Pat. No. 3,504,074, of Mar. 31, 1970, apparatus of the abovesummarized type is disclosed that has successfully met the requirementsof volume production of containers of which egg cartons are but oneexample. In that patent, the shafts for the sprockets about which weretrained corresponding ends of the chains of the two conveyors aregear-connected and the indexing means are operative to turn a disc faston one of those shafts. This arrangement did not permit the step lengthto be varied and lead to the indexing means disclosed in applicationSer. No. 13,631, filed Feb. 24, 1970, owned by applicants assignee andoperating in a generally similar manner but permitting of adjustments ofthe step length.

While the above referred to indexing means have successfully metproduction requirements, they have not entirely eliminated thepossibility of small errors in step length which, because of the numberof steps required, lead occasionally to printing, blanking, or bothoperations being inaccurately performed. Some articles, includingseveral types of egg cartons, for example, can tolerate small steppingerrors in their production while others, those, for example, havingclosely fitting covers, must be held to tolerances closer than havehitherto been possible to establish and maintain. The failure of theabove referred to indexing means to be precisely uniform is due toseveral factors such as play between the sprockets and chains and chainstretching either due to temperature changes or to the repeated pull ofthe indexing means.

The general objective of the present invention is, accordingly, toprovide indexing means for conveyors that enable accurate steps to beestablished and maintained, an objective attained by providing indexingapparatus having a base provided with a support reciprocable between twolimits and provided with chain grabbing means. Means are provided toreciprocate the support between the two limits to effect predeterminedtravel of the grabbing means lengthwise of the conveyor and to renderthe grabbing means effective only during travel thereof from one limitto the other in one direction thus to positively effect a steppedadvance of the conveyor that is accurately measured. The base isprovided with means to lock the conveyor against movement for apredetermined dwell during which the support is returned into positionfor the next step.

Another objective of the present invention is to provide means that willensure that the conveyor is subject to a constant endwise tension byfluid pressure operated means and when both supporting and holddownconveyors are used, to ensure that both are equally tensioned.

Another objective of the invention is to provide apparatus in which thetravel of the support for the grabbing means is accelerated at thecommencement of each step and a retarded rate at the end thereof tominimize chain stretching and jamming.

And yet another objective of the invention is to provide that theconveying means include an additional chain trained about sprocketscoaxial with the sprockets in support of the chains of the conveyor withthe grabbing means including at least one tooth engageable therewith toensure a positive hold. In practice, the grabbing means include twodevices, one at each side of the conveying means and the conveying meansincludes an additional chain at each side, the additional chains beingon the outside. When the conveying means includes both hold-down andsupporting conveyors, each conveyor has such additional chains and eachgrabbing device clamps together the proximate course thereof at itsside. Preferably means are employed to yieldably urge the proximatecourses of the other chains together to ensure the effective gripping ofthe margins of the sheet material to ensure its advance and to hold itagainst warping as in the case of a heated plastic sheet.

In the accompanying drawings, there is shown an embodiment of theinvention illustrative of these and other of its objectives, novelfeatures, and advantages.

In the drawings:

FIG. 1 is a plan view of the indexing station of apparatus for advancingmaterial step-by-step through a series of stations at which, duringdwells, operations are performed thereon;

FIG. 2 is a side view of the reciprocable support and the chaintensioning means;

FIG. 3 is a side view of the indexing station broken away to foreshortenthe drawing and with parts of the reciprocable support also broken away;

FIG. 4 is a side view, on an increase in scale, of one of the chaingrabbing devices;

FIG. 5 is a section taken vertically through the device shown in FIG. 4;I

FIG. 6 is a section taken approximately along the indicated lines 6-6 ofFIG. 1;

FIG. 7 is a section taken approximately along the indicated lines 7-7 ofFIG. 1;

FIG. 8 is a section, on a further increase in scale, taken approximatelyalong the indicated lines 8-8 of FIG. 1;

FIG. 9 is a plan view of one of the chain tensioning devices;

FIG. 10 is a side view thereof;

FIG. 11 is a section taken approximately along the indicated lines 11-11of FIG. 10;

FIG. 17 is a schematic view of the pneumatic circuitry in control of thegrabbing devices;

FIGS. 18 and 18A are schematic views of the hydraulic circuitry; and

FIG. 19 is a fragmentary schematic view showing that part of theelectric circuitry concerned with indexmg.

As the indexing means of the present invention may be illustratedwithout detailing stations to which articles are to be successivelyconveyed by the step-by-step operations of the conveyor means, acomplete apparatus is not shown. The description of all features of theindexing means and of the preferred conveying means makes it convenient,however, to make reference to article forming and blanking stationsindicated generally at 20 and 21, respectively, in FIGS. 18 and 18A withthe conveyed material being a heated plastic sheet generally indicatedat 22 in certain of the drawings, and with the conveying meanscomprising supporting and hold-down conveyors generally indicated at 23and 24, respectively, which grip the margins of the sheet material 22between them as it is conveyed to and through the article formingstation 20 and thereafter, at least until it has sufficiently cooled toavoid warpage of the articles when blanked therefrom. The indexingstation is generally indicated at 25.

The article forming station 20 is shown schematically in FIG. 18 ashaving a lower and upper pair of hydraulically operated piston-cylinderunits indicated at 26 and 27, respectively, operable to bring molds intoand out of article-forming contact with opposite faces of the sheetmaterial during a dwell. The operation of the units 26 and 27 iscontrolled by solenoid operated valves 28.

The sheet material 20 is then advanced step-by-step until it issufficiently cool to permit the articles to be blanked therefrom at theblanking station 21, shown as having an upper hydraulically operated,piston-cylinder unit 29 and a lower like unit 30 for blanking diesoperable to blank the formed articles from the sheet positioned betweenthem at a dwell. The units 29 and 30 have their operation controlled bysolenoid operated valves 31.

Intermediate stations such as printing station are omitted both tosimplify the drawings and because intermediate operations are not alwaysperformed on the articles. As the circuitry for controlling thesolenoids of the valves 28 and 31 form no part of the present invention,it is not shown.

The apparatus has a base common to the several stations of which itsupper sides 32 are provided with supports, generally indicated at 33,for vertically spaced double sprockets 34 about appropriate ones ofwhich the chains of the supporting and hold-down conveyors are trained.For convenience, only the sprocket supports 33 for the outfeed ends ofthe conveyors are shown and these are detailed in FIGS. 7, 9, 10, and 11.

Each sprocket support 33 includes a housing 35 in which verticallyspaced shafts 36 are rotatably mounted, each shaft provided with adouble sprocket 34. Each housing 35 has a base plate 37, see FIGS. 2 and7, slidable in a transverse slideway 38 mounted on the subjacent rail 32and each plate 37 has a depending arm 39 provided with a nut 40 throughwhich is threaded one end portion of a shaft 41 extending transverselyof the base below the side 32 and rotatably supported thereby. The nutsand threaded shaft portions at one side of the conveyor are of a handopposite to those at the other side of the conveyor so that by turningthe shaft 41 in one direction or the other, the spacing between the twosprocket supports 33 may be adjusted as required by the width of thesheet material 22 being processed. The supports 33 at the infeed ends ofthe conveyor are similar, as thus far described, and hence are notshown.

The supports 33 at the outfeed end of the apparatus have each of theirshafts 36 supported by slides 42 each including end key portions 43slidably entrant of slideways 44 in the side walls 45 of the housings 35with the slideways provided with central, elongated portions 46permitting sliding movement of the shafts 36. Each slide 42 has avertical slot 47 by which bearing plates 48 are secured in verticallyspaced relationship. Each support 33 at the outfeed end of the conveyorhas a piston-cylinder unit 49 attached thereto with its stem 50extending between the plates 48 and having a pressure member 51centrally pivoted thereto as at 52. The piston-cylinder unit 49 isconnected, see FIG. 18A, to one of the hydraulic pressure sources 53 bya conduit 54 provided with an adjustable valve 55. With such means, adesired chain-tensioning pressure is maintained on the chains of bothconveyors and the centrally pivoted pressure member 51 is operative toequalize such pressures.

The conveyors 23 and 24 are best seen in FIGS. 12

16. The supporting conveyor 23 has a transversely spaced pair of rollerchains, the inner chains being indicated at 56 and the outer pair ofchains at 57. Each chain of the conveyor 23 has rollers 58interconnected by inner links 59 and outer links 60. The inner links 59at the inside of the chains and the outer links 60 at the outside of thechains have inturned flanges providing seats 61 and 62, respectively,along the upper surface of their upper course in support of the sheetmaterial The hold-down conveyor 24 also has transversely spaced pairs ofroller chains with the inner chains indicated at 63 and the outer chainsat 64. Each chain of the conveyor 24 has rollers 65 interconnected byinner links 66 and outer links 67. Both sets of inner links 66 of eachof the chains 63 and 64 have projecting teeth 68 disposed to bedownwardly disposed in their lower courses thus to provide means forpositively gripping the margins of the sheet 22 against the supportingsurface provided by the seats 61 and 62 of the chains of the conveyor23.

The remote courses of the chains of the conveyors 23 and 24 areprotected by shields 69 and 70, respectively, secured at their ends tothe sprocket supports 33 and these serve as a means for mounting shoes71 and 72 ensuring that the proximate courses of the inner chains of theconveyors 23 and 24 are held in a sheet gripping relationship. Inpractice the inner shoes 71 and the shoes 72 are spaced along the fulllength of the conveyors except in the zone of the locking means. As maybe seen in subsequently to be described FIGS. 12 14, the shields 69 andare interconnected by pairs of vertical members 73 to the inner face ofeach pair of which a lower bar 74 is secured. Each bar 74 has a pair ofinwardly disposed bolts 75 supporting a pair of shoes 71 spaced fromeach other and dimensioned so that each supports a chain of the conveyor23 by the rollers thereof. An upper bar 76 is slidably supported on theinner faces of the members 73 by keepers 77. At each end of each lowerbar 74 there are supports 78 for eyes 79 to which the lower ends oftension springs 80 are attached. The upper ends of the springs 80 aresecured by pins 81 to the upper bar 74 which has bolts 82 supporting asingle shoe 72 dimensioned to ride on the rollers of the inner chains 63of the upper or hold-down conveyor 24 with the springs 80 ensuring theefiective gripping of the margins of the sheet material 22 between thetwo conveyors. The outer chains 64 of the conveyor 24 are not held down.

In FIG. 1 the base is shown as having an inner frame 83 provided withend mounts 84 and 85 including seats 86 and 87, respectively. The endsof a tubular stem 88 of a piston-cylinder unit 89 are secured by themounts 84 and 85. The piston-cylinder unit 89 is of the doubleactingtype and each end of the stem 88 has a conduit secured thereto, theconduit 90 for effecting forward indexing of the conveyors and theconduit 91 for effecting the reset position of the indexing means. Theconduits 90 and 91 are connected to one of the sources 53 of liquidunder pressure by a four-way valve 92 set in an indexing position by thesolenoid 93 and in a resetting position by the solenoid 94, see FIG. 19.

In addition, the conduit 90 is provided with a valve 95 mounted on theframe 83 and having its stem 96, see FIG. 6, actuated by a cam 97mounted on one side of a support 98 for adjustment relative to the fixedscale 99, see FIG. 3. That side of the support 98 is also provided withcams 100 and 101 arranged to operate limit switches 102 and 103,respectively, also mounted on the frame 83. The cam 101 is secured tothe cam 97 so that it is adjusted therewith.

The support 98 is connected to the cylinder of the unit 95 by carriages104. Each carriage 104 has upper side rollers 105 whose axes areoutwardly and downwardly inclined and lower side rollers 106 whose axesare outwardly and upwardly inclined. Vertically connected tracks 107 and108 at each side of the carriage are supported by the frame 83 and aredisposed at the appropriate angle for engagement by the appropriaterollers of the carriages thus ensuring free travel of the support 98between the seats 86 and 87, the distance between which defining themaximum step length. The carriages 104 have contact heads 109 forengagement with an appropriate one of the seats. The step length may bevaried as by means of stops detachably mounted on the stem 88 to beengaged by and limit travel of the carriage 98 in a resetting direction.Conveniently the stops are of different lengths with the smallestrepresenting a predetermined minimum adjustment of the step length andthe others being different multiples thereof, the stops 110 and 111, forexample. Each stop may comprise sections clamped together about the stem88 by means of screws and when such stops are employed it is necessaryto make appropriate adjustments in the location of the cams 97 and 101lengthwise of the support 98. The graduations of the scale 99 are eachequal to the thickness of the smallest stop 110 and the support has,below that side, a series of threaded bores 112 for the screws 113 bywhich the cam 97 is held in place, the threaded bores 112 being spacedapart by the same distance as the graduations of the scale.

It will be noted that the support 98 is provided with chain grabbingdevices generally indicated at 114, one for the chains at each side ofthe conveyors. The construction of the chain grabbing devices 114 isshown in FIGS. 4 and 5 with each consisting of a housing 115 to whichthe cylinder of a pneumatically operated pistoncylinder unit 116 isattached with its stem 117 secured to a block 118 slidably supported inthe housing on vertically spaced rods 119, the block 118 having a pairof complemental cam tracks 120 and 121 in one side. Chain grabbing jaws122 have cam followers 123 each entrant of an appropriate one of theaforesaid cam tracks. The jaws 122 are confined within a slideway 124with which the housing 115 is provided for vertical movement between anopen position in which the proximate courses of the outside chains ofboth conveyors are between them but free and a closed position in whichsaid courses are grabbed. It should be here noted that throughout themaximum distance the chain grabbing devices 114 may travel, the outershoes 71 are omitted, see FIGS. 5 and 14, so that the proximate coursesof the outer chains may be received between the jaws 122. As shown inFIG. 17, the units 116 are both connected to a suitable source 125 ofair under pressure by conduits 126 controlled by a valve 127 that isnormally set to maintain the jaws 122 in their chain grabbing positionsbut is operated by a solenoid 128, see FIG. 19, to effect the movementof the jaws into their open, chain-releasing positions.

Each jaw 122 is provided with a series of teeth 129 disposed anddimensioned for entry between the rollers of the chain which it engages.It will be appreciated, that when the jaws 122 are in their operativerelationship, their teeth 129 fit snugly between chain rollers tosecurely lock proximate courses of the outside chains to the support 98.When the piston-cylinder unit 89 is actuated to shift the support 98 inthe direction of the arrow in FIG. 1 from its reset position in whichthe head 109 of one carriage 104 is held against the seat 86 or a stopbacked thereby until it reaches the other limit of its travel in whichthe head 109 of the other carriage is held against the seat 87 at theother end of the frame 83. As the distance the slide 98 can travel isaccurately established, the conveyors and the sheet material are alsopositively advanced for the exact predetermined distance. Each housing115 is connected to the support 98 by bolts 130 extending through slots131 extending transversely thereof to enable their position to be ad- 65justed to vary the spacing between them as required by therewith whenthe width of the conveyors is varied. Each locking device 132 is locatedoutside the conveyors and, see FIG. 8, has a mount 133 provided with alengthwise channel 134 shown as receiving only the outer chains of theproximate courses thereof. The cylinder of a piston-cylinder unit 135 issecured to the mount 133 with it axis in the plane of the sheet 22 andat right angles to the chains. The stem 136 of the unit 135 is connectedto a head 137 slidable in a bore 138 intersected by a vertical slot 139opening through the inner end of the mount 133. The head 137 has grooves140 receiving the ends of upper and lower bell crank levers 141pivotally mounted in the slots 139 by pins 142. The slot 139 isinterconnected by lengthwise vertical slots 143 slidably confining upperand lower locking members 144. The locking members 144 are supported bythe other ends of the levers 141 so that they are movable between aninoperative position in which the outer chains are free into anoperative position in which they are both locked against moving. Eachlocking member 144 has a series of teeth 145 which like the teeth 129 ofthe grabbing devices are disposed and dimensioned to fit snugly betweenthe rollers of the chain it engages. The locking devices 132 secure thechains and accordingly the sheet material 22 against movement duringdwells at which time various operations may be made on the materialbeing conveyed. The units 135 have their conduits 146 and 147 connectedto a source 53 of liquid under pressure by a four way valve 148, seeFIG. 18A, set in a locking position by the solenoid 149, and in a chainreleasing position by a solenoid 150, see FIG. 19.

The operation of the indexing apparatus can best be discussed inconnection with the electric circuitry schematically shown in FIG. 19 inwhich only that part thereof that is concerned with indexing is shown.

A generally indicated circuit 151 includes a control switch 152 and hasa series of parallel leads of which the lead 153 includes the normallyclosed switch 154 of the timer 155, a branch lead 156 and a series ofswitches of which the switches 157 and 158 are closed when thepiston-cylinder units 26 and 27 at the articleforming station 20 are intheir retracted, inoperative positions. The series also includesswitches 159 and 160, closed when the piston-cylinder units 29 and 30 atthe blanking station 21 are in their retracted, inoperative positions,the normally open switch 103A of the limit switch 103 closed when thesupport 98 is in its reset position, and the relay 162. The branch lead156 includes the normally closed switch 163 of the relay 164 and thesolenoid 150 effecting the chain-releasing positions of the lockingdevices 131. The lead 165 has the normally open switch 166 of the relay162, the normally closed switch 167 of the relay 164 and the relay 162.

it will thus be apparent that if the operations at the stations havebeen completed, the time controlled dwell terminated and the support 98in its reset position, the circuit to the timer 155 is open as willpresently be described, the lead 153 is closed to energize the relay 162with its switch 166 now closed so that the lead 165 serves as a holdingcircuit therefor.

The lead 167 has parallel leads 168 and 169 with the branch lead 168having the normally open switch 170 of the relay 162 and the solenoid 93by which the valve 92 is set to cause indexing.'The lead 169 is providedwith the normally closed switch 171 of the relay 162 and the solenoid 94by which the valve 92 is shifted to effect resetting of the support 98.

Assuming that the operations at the stations have been completed withthe switches 157, 158, 159, and 160 closed and the support 98 in itsreset position so that the switch 161 is also closed, the relay 162 isenergized. As a consequence, the relay switch 103 is now closed with thesolenoid 93 energized and the relay switch 171 is open. The normalstatus of the grabbing device 114 is that the jaws 122 are in theirclosed, chain grabbing positions. The support 98 now moves forwardlycarrying the conveyor chains with it until its other limit of travel isreached.

The lead 172 has the limit switch 102 closed when the support 98 reachessaid other limit of travel and the relay 164 which is now operable toopen the switch 167 in the holding circuit for the relay 162. The lead174 has the normally open switch 175 of the relay 164 and the timer 155so that with the relay 164 energized, the

switch closes and the timer 155 is started and the switch 154 is thenopened. An important feature of the invention is that the switch 167 isof the type having a brief predetermined time delay before it opens.When the relay 164 is energized, the switch 163 is instantly openedwhile the relay 162 is held energized for a brief interval delayingresulting reset travel of the support 98.

The lead 176 has the normally open timer switch 177 and the normallyclosed switch 103B of the limit switch 103 cammed open by the cam 101when the support 98 reaches its reset position, and the parallel leads179, 180, and 181. The lead 179 includes the solenoid 149 which isenergized to lock the chains against movement, such locking occurringbefore the resetting of the indexing means because of the time delayfeature of the switch 167. The lead 180 includes the solenoid 128 whichis now energized to cause the grabbing devices to release the chains.The lead 180 includes a relay 182 operable to close its normally openswitch 183 in the holding lead 184. The lead 185 includes the normallyopen switch 186 of the timer 155 thus to serve as a holding circuittherefor and for the relay 187 in parallel with the timer 155 andcontrolling other circuitry to enable operations at other stations to beperformed during a dwell. Thus, at the end of a step, the grabbingdevices 114 are released and the locking devices 132 energized to lockthe chains, and the support 98 then returned to its reset position.

At the end of the resulting reset travel of the support 98, the cam 101on the support 98 again closes the limit switch 103A but the solenoid162 cannot be again energized until the end of the timed dwell and theother limit switches in the lead 153 are closed. At the end of thedwell, the chain locking device 132 releases the chains.

Reference is now made to the utility of the valve 95. It will be seenfrom FIGS. 3 and 6 that as the end of the reset travel of the support 98nears, the cam 97 moves the valve 95 to partially close it thus todecelerate the support 98 and to provide that at the commencement of thenext step, its indexing travel will be accelerated after aninitial'relatively slow start thus protecting the conveyor chainsagainst stretching. It is also desirable IOIOSZ 0526 to provide likedeceleration of the support as the end of an indexing step is reached.This result is attained by means of a cam 97A so located, see FIG. 3, asto operate the valve 95 in the manner of the cam 97 as the end of a stepis approached.

From the foregoing, it will be apparent that indexing apparatus inaccordance with the invention are well adapted to meet the requirementsof ensuring precision steps with misalignment of the chain linksprevented by constant, equalized tensioning of the conveyors, and withthe acceleration and deceleration of the support 98 provided in bothdirections of its travel.

We claim:

1. Indexing apparatus comprising conveying means, a base, a supportconnected to said base for movement between two limits defining a stepand including means to grab said conveying means, means operable toreciprocate said support between said limits to effect travel of saidgrabbing means lengthwise of the conveying means, means operable torender said grabbing means effective during travel thereof from onelimit to the other in one direction thereby to effect a stepped advanceof said conveyor, means to lock the conveying means against travelling,and control means to effect the operation of the reciprocating meanswhen it reaches either limit and of the locking means during travel ofthe support in its resetting direction, said control means including atimer operable when the support is at the end of a step to provide apredetermined delay before another advancing step results from itsresetting travel.

2. The indexing apparatus of claim 1 in which the timer is set inoperation at the end of each step and provides an operating cycle inwhich first the locking means are rendered operative, the reciprocatingmeans are then operated in the support resetting direction, and finallythe reciprocating means operated to advance the support for anotherstep.

3. The indexing apparatus of claim 2 in which the grabbing means isnormally operative and the control means renders the grabbing meansinoperative during resetting travel of the support.

4. The indexing apparatus of claim 1 in which the base includes means tolock the conveying means, timer-controlled means to render said lockingmeans operative on travel of the grabbing means in the other directionand to provide a dwell, adjustable means to vary the infeed limitrelative to the outfeed limit, and adjustable means operable to vary theoperation of the grabbing and the release of the locking means inrelation to the adjusted infeed limit.

5. The indexing apparatus of claim 1 in which the base includeslengthwise tracks and the means connecting the support to the baseinclude marginal rollers in engagement with the tracks.

6. The indexing apparatus of claim 1 in which there is a lower pair oftracks that are both outwardly and upwardly inclined and an upper pairof tracks that are both inwardly and upwardly inclined and the axes ofthe rollers are inclined as required by the engaged track.

7. The indexing apparatus of claim 1 and stops attachable to the sternof the piston-cylinder unit to be then backed by the proximate seat, onestop being of a predetermined axial extent and the axial extent onanother stop being a multiple thereof.

8. The indexing apparatus of claim 7 and conduits for liquid underpressure in communication with opposite ends of the cylinder of the unitand including a fourway valve, a pair of solenoids connected to saidvalve, one operable to set said valve to efiect indexing travel of thesupport and the other operable to effect resetting travel thereof, limitswitches mounted on the base, one for each solenoid and in controlthereof, and cams one adjacent each end of the support and attachedthereto and operable to engage and actuate the appropriate one of saidlimit switches at the end of support travel in a predetermineddirection.

9. The indexing apparatus of claim 8 and means to adjust the travel ofthe support relative to its reset position, and means to adjust theposition of the cam actuating the limit switch at the end of resettravel of the support lengthwise thereof by increments equal to themaximum axial extent of a stop.

10. The indexing apparatus of claim 9 and a regulating valve in controlof one of the conduits, and a cam associated with the cam operable atthe end of reset travel of the support and adjustable therewith, saidassociated cam being operable to actuate the regulating valve todecelerate the rate of support travel as the support arrives at andleaves its reset position.

11. The indexing apparatus of claim 10 and a cam associated with the camoperable at the end of the indexing travel of the support and operableto actuate the regulating valve to decelerate and accelerate the rate ofsupport travel as the support arrives at and leaves the seat at theoutfeed end of the conveyor means.

12. The indexing apparatus of claim 1 in which the control means effectslocking engagement of thegrabbing means with the conveying means onlyfrom the time when the support is in its reset position until it hascompleted a step and the control means is operable to render the lockingmeans operable to hold the conveying means when the support is in itsreset position but before the resetting travel of the support isinitiated and to continue operable until the end of the timed interval.

13. The indexing apparatus of claim 1 in which the reciprocating meansincludes a double-acting, pistoncylinder unit, a source of liquid underpressure, and a valve including a control movable between positionseffecting low and high speed travel of the support, and means carried bysaid support to actuate said control from its high speed position to itslow speed position from the time it approaches its reset position untilafter it has left that position to effect another step.

14. The indexing apparatus of claim 13 in which the support alsoincludes means to actuate the control from its high speed position toits low speed position from the time it approaches the end of a stepuntil after it has left that position towards its reset position.

15. Indexing apparatus comprising a base, conveying means mounted onsaid base and including supporting and hold-down conveyors, bothincluding endless, transversely spaced chains with their proximatecourses disposed to receive sheet material between them, each one of theconveyors including endless outer chains at each side, sprockets insupport of all chains of each conveyor, the sprockets for the additionalchains being axially connected to the corresponding sprockets of theappropriate one of the conveyors, a support connected to said base formovement between two limits defining a step and including a grabbingdevice at each side of the conveyor means and operable to grab togetherthe proximate courses of the additional chains at that side, meansoperable to reciprocate said support between said limits to effecttravel of said grabbing means lengthwise of the conveying means, meansoperable to render said grabbing means effective during travel of saidsupport from one limit to the other in one direction thereby to effect astepped advance of said conveying means and means operable to lock saidadditional chains to said base during resetting travel of the support.

16. The indexing apparatus of claim 15 in which each grabbing devicecomprises a mount having a vertical slideway extending lengthwise of theconveying means, a pair of jaws in said slideway, each jaw including acam follower, and fluid pressure operated means attached to said mountand provided with a head reciprocable therein, the head having a pair ofcam tracks, each receiving a cam follower'and inclined towards eachother, whereby on reciprocation of said head, the jaws are moved intoand out of a closed position, each device being disposed with theproximate courses of the appropriate additional chains between the jaws.

17. The indexing apparatus of claim 16 in which the jaws include aplurality of teeth disposed towards each other and shaped anddimensioned to fit snugly between rollers of the additional chains.

18. The indexing apparatus of claim 15 and fluid pressure operated meansoperable to lock the additional chains against movement at least whilethe support is travelling in a resetting direction, the locking meanscomprises a pair of locking devices, one at each side of the conveyingmeans, each device comprising a mount, a piston-cylinder unit attachedto said mount with its axis at right angles to the direction of travelof the conveying means, a pair of jaws, one below and one above theproximate courses of the additional chains, bell cranks each pivotallysupported by said mount with one end connected to the stem of said unitand with its other end in support of an appropriate one of the holders.

19. The indexing apparatus of claim 18 in which each jaw has a series ofteeth disposed and dimensioned for snug entry between the rollers of theadditional chains.

20. The indexing apparatus of claim 15 and conveyor tensioning meansconnected to both conveyors and operable to maintain an equalizedtension thereon.

21. The indexing apparatus of claim 15 and shoes supporting the uppercourses of the chains of the supporting conveyor and shoes yieldablyurging the lower courses of the chains of the hold-down conveyordownwardly into gripping relation with the subjacent conveyor chains,and shoes supporting the upper courses of the additional chains exceptin the zone of travel of the grabbing devices.

1. Indexing apparatus comprising conveying means, a base, a supportconnected to said base for movement between two limits defining a stepand including means to grab said conveying means, means operable toreciprocate said support between said limits to effect travel of saidgrabbing means lengthwise of the conveying means, means operable torender said grabbing means effective during travel thereof from onelimit to the other in one direction thereby to effect a stepped advanceof said conveyor, means to lock the conveying means against travelling,and control means to effect the operation of the reciprocating meanswhen it reaches either limit and of the locking means during travel ofthe support in its resetting direction, said control means including atimer operable when the support is at the end of a step to provide apredetermined delay before another advancing step results from itsresetting travel.
 2. The indexing apparatus of claim 1 in which thetimer is set in operation at the end of each step and provides anoperating cycle in which first the locking means are rendered operative,the reciprocating means are then operated in the support resettingdirection, and finally the reciprocating means operated to advance thesupport for another step.
 3. The indexing apparatus of claim 2 in whichthe grabbing means is normally operative and the control means rendersthe grabbing means inoperative during resetting travel of the support.4. The indexing apparatus of claim 1 in which the base includes means tolock the conveying means, timer-controlled means to render said lockingmeans operative on travel of the grabbing means in the other directionand to provide a dwell, adjustable means to vary the infeed limitrelative to the outfeed limit, and adjustable means operable to vary theoperation of the grabbing and the release of the locking means inrelation to the adjusted infeed limit.
 5. The indexing apparatus ofclaim 1 in which the base includes lengthwise tracks and the meansconnecting the support to the base include marginal rollers inengagement with the tracks.
 6. The indexing apparatus of claim 1 inwhich there is a lower pair of tracks that are both outwardly andupwardly inclined and an upper pair of tracks that are both inwardly andupwardly inclined and the axes of the rollers are inclined as requiredby the engaged track.
 7. The indexing apparatus of claim 1 and stopsattachable tO the stem of the piston-cylinder unit to be then backed bythe proximate seat, one stop being of a predetermined axial extent andthe axial extent on another stop being a multiple thereof.
 8. Theindexing apparatus of claim 7 and conduits for liquid under pressure incommunication with opposite ends of the cylinder of the unit andincluding a four-way valve, a pair of solenoids connected to said valve,one operable to set said valve to effect indexing travel of the supportand the other operable to effect resetting travel thereof, limitswitches mounted on the base, one for each solenoid and in controlthereof, and cams one adjacent each end of the support and attachedthereto and operable to engage and actuate the appropriate one of saidlimit switches at the end of support travel in a predetermineddirection.
 9. The indexing apparatus of claim 8 and means to adjust thetravel of the support relative to its reset position, and means toadjust the position of the cam actuating the limit switch at the end ofreset travel of the support lengthwise thereof by increments equal tothe maximum axial extent of a stop.
 10. The indexing apparatus of claim9 and a regulating valve in control of one of the conduits, and a camassociated with the cam operable at the end of reset travel of thesupport and adjustable therewith, said associated cam being operable toactuate the regulating valve to decelerate the rate of support travel asthe support arrives at and leaves its reset position.
 11. The indexingapparatus of claim 10 and a cam associated with the cam operable at theend of the indexing travel of the support and operable to actuate theregulating valve to decelerate and accelerate the rate of support travelas the support arrives at and leaves the seat at the outfeed end of theconveyor means.
 12. The indexing apparatus of claim 1 in which thecontrol means effects locking engagement of the grabbing means with theconveying means only from the time when the support is in its resetposition until it has completed a step and the control means is operableto render the locking means operable to hold the conveying means whenthe support is in its reset position but before the resetting travel ofthe support is initiated and to continue operable until the end of thetimed interval.
 13. The indexing apparatus of claim 1 in which thereciprocating means includes a double-acting, piston-cylinder unit, asource of liquid under pressure, and a valve including a control movablebetween positions effecting low and high speed travel of the support,and means carried by said support to actuate said control from its highspeed position to its low speed position from the time it approaches itsreset position until after it has left that position to effect anotherstep.
 14. The indexing apparatus of claim 13 in which the support alsoincludes means to actuate the control from its high speed position toits low speed position from the time it approaches the end of a stepuntil after it has left that position towards its reset position. 15.Indexing apparatus comprising a base, conveying means mounted on saidbase and including supporting and hold-down conveyors, both includingendless, transversely spaced chains with their proximate coursesdisposed to receive sheet material between them, each one of theconveyors including endless outer chains at each side, sprockets insupport of all chains of each conveyor, the sprockets for the additionalchains being axially connected to the corresponding sprockets of theappropriate one of the conveyors, a support connected to said base formovement between two limits defining a step and including a grabbingdevice at each side of the conveyor means and operable to grab togetherthe proximate courses of the additional chains at that side, meansoperable to reciprocate said support between said limits to effecttravel of said grabbing means lengthwise of the conveying means, meansoperable to render said grabbing means effective during travEl of saidsupport from one limit to the other in one direction thereby to effect astepped advance of said conveying means and means operable to lock saidadditional chains to said base during resetting travel of the support.16. The indexing apparatus of claim 15 in which each grabbing devicecomprises a mount having a vertical slideway extending lengthwise of theconveying means, a pair of jaws in said slideway, each jaw including acam follower, and fluid pressure operated means attached to said mountand provided with a head reciprocable therein, the head having a pair ofcam tracks, each receiving a cam follower and inclined towards eachother, whereby on reciprocation of said head, the jaws are moved intoand out of a closed position, each device being disposed with theproximate courses of the appropriate additional chains between the jaws.17. The indexing apparatus of claim 16 in which the jaws include aplurality of teeth disposed towards each other and shaped anddimensioned to fit snugly between rollers of the additional chains. 18.The indexing apparatus of claim 15 and fluid pressure operated meansoperable to lock the additional chains against movement at least whilethe support is travelling in a resetting direction, the locking meanscomprises a pair of locking devices, one at each side of the conveyingmeans, each device comprising a mount, a piston-cylinder unit attachedto said mount with its axis at right angles to the direction of travelof the conveying means, a pair of jaws, one below and one above theproximate courses of the additional chains, bell cranks each pivotallysupported by said mount with one end connected to the stem of said unitand with its other end in support of an appropriate one of the holders.19. The indexing apparatus of claim 18 in which each jaw has a series ofteeth disposed and dimensioned for snug entry between the rollers of theadditional chains.
 20. The indexing apparatus of claim 15 and conveyortensioning means connected to both conveyors and operable to maintain anequalized tension thereon.
 21. The indexing apparatus of claim 15 andshoes supporting the upper courses of the chains of the supportingconveyor and shoes yieldably urging the lower courses of the chains ofthe hold-down conveyor downwardly into gripping relation with thesubjacent conveyor chains, and shoes supporting the upper courses of theadditional chains except in the zone of travel of the grabbing devices.